Integrated River Basin Management (IRBM): Simulation Modeling System for Kurau River Sub-basin

A river basin is an area delineated by its natural hydrological boundaries such that any rain falling on the area will drain to the river. Any activity that takes places upstream of a river basin will eventually have an impact on the quality and quantity of the river water as its reaches the downstream. Realizing the seriousness of the problems and the threat it may pose to the environment, Malaysia has embarked on a journey to practise Integrated River Basin Management (IRBM) particularly to strengthen the sustainable management of the country’s natural resources. In this study, Kurau River sub-basin was selected to determine the effect of the landuse changes to water quality of Kurau River sub-basin in order to support the implementation IRBM by using Soil and Water Assessment Tools (SWAT2005) and Hydrologic Engineering Centre-Hydrologic Modelling System (HEC-HMS) mathematical models and integrates with GIS to produce spatial input data in model. This study also estimate sediment yield using SWAT2005 and to determine the suitability of HEC-HMS and SWAT2005 as Decision Support System Tools for IRBM. Two scenarios were set to stimulate the landuse behaviours in Kurau River Sub-basin in term of runoff hydrograph and sediment yield using United States Soil and Conservation Services (SCS) method. Landuse in 2004 and 2015 were used to perform the simulations. First scenario is according to the planning by Town Planning Department for Larut Matang 2015 Local Plan then second scenario is assumed that the entire sub-basins were having 20% increase of CN. Both scenarios were applied using HEC-HMS and SWAT2005 model. Scenario simulation Follow Larut Matang 2015 Local Plan produces an increase of peak flow at Pondok Tanjung Station by 4.67% (3.20m₃/s) as compared to Batu 14 station by 20.40% (1.90m₃/s). Meanwhile for scenario simulation 20% increase of CN for all Sub-Basins results shows an increase of peak flow at Pondok Tanjung station by 20.46% (14.00m₃/s) compare at Bt 14 station by 35.48% (3.30m₃/s). Scenario simulation by 20% development for all subbasin for SWAT2005 also shows an increase of peak flow by 6.06% (15.14m₃/s) compare to scenario follow Larut Matang 2015 Local Plans shows an increase of peak flow by 1.92% (4.80m₃/s). As for the suspended sediment, scenario simulation by 20% increase of CN for all sub-basins shows an increase of sediment by 80.88% (16,887.39 tonnes/day) compare to scenario follow Larut Matang2015 Local Plan shows an increase of sediment by 50.86% (11,454.75 tonnes/day). The result shows that landuse 2015 are suitable for future planning in Kurau River Sub-basin in term of hydrology but suspended sediment shows an increase. Proper planning by responsible agencies should be taken in order to avoid the negative environmental impact on landuse in Kurau River Sub-basin. Result also demonstrated that HEC-HMS and SWAT2005 is a modelling tool for analyzing hydrological processes and water quality planning and management in the Kurau River Sub-basin.